1. Field of the Invention
The present invention relates to an apparatus for generating and supplying clock signal having a Long term jitter noise removed therefrom to each device in a mobile communication terminal containing the apparatus and having a power management chip mounted thereto for converting a sinusoidal wave oscillated in a crystal to generate a clock signal of square wave.
2. Description of the Prior Art
A jitter noise occurring in a wireless circuit is meant by a kind of distortion phenomenon that an output signal vibrates for a time axis. Due to the jitter noise, an output signal in a time area is outputted after a predetermined delay time. In addition, a waveform of the output signal in a frequency area is dispersed to the neighborhood of a specific frequency, instead of being formed sharply in the specific frequency. The jitter noises can be classified into a Cycle to cycle jitter noise as shown in FIG. 1(a), a Period jitter noise as shown in FIG. 1(b) and a Long term jitter noise as shown in FIG. 1(c) according to shapes of an output signal distorted due to the jitter noise.
In the mean time, in mobile communication terminals of GSM (Global System for Mobile communication)/CDMA (Code Division Multiple Access)/WCDMA (Wideband Code Division Multiple Access) types, most of power management chips use a crystal as an oscillator. At this time, the jitter noises as shown in FIGS. 1(a) to 1(c) can occur in a clock signal outputted from the power management chip. In particular, the ‘long term jitter noise’ as shown in FIG. 1(c) which is mainly induced in a power supply of the oscillator using the crystal causes a time difference in the waveform of the clock signal. Owing to the time difference, the clock signal supplied to each device, such as baseband processor, memory and the like in the mobile communication terminal is not synchronized, so that there may occur a driving error in each device.